This Is What Really Happens When You Put Diesel in a Gas Car

Updated: Jan. 27, 2023

The damage to your car’s engine will be severe and expensive to fix — if it can be fixed.

Refueling car at gas station. Filling fuel.Krasula/Shutterstock

What Happens When You Put Diesel in a Gas Car?

Accidentally putting diesel into a car that runs on gasoline doesn’t happen that often, but when it does it can do a lot of damage to your vehicle and your wallet. Check out these five inexpensive car additives could save you a ton of money.

Plus, learn these things that you may be doing that are shortening the life of your car:

Different Nozzle Sizes

First, if you’re worried this is going to happen to you, don’t be — it’s hard to fill up your car with diesel if it takes gasoline. The nozzle on diesel pumps is typically bigger, so it won’t fit in your gas tank. And normally it’s green, and at a separate, clearly-labeled pump. Put your phone away so you’re not distracted and check to see that everything looks normal before pumping your gas. To make sure you don’t run into any other costly car problems, check out these maintenance tips that will extend the life of your car.

Diesel Fuel Can Cause Clogs

To most people, diesel and gasoline might seem like similar substances. Both come from a pump at a gas station, right? But they’re not. “Diesel is a much thicker substance than traditional gasoline and it is ignited by pressure rather than a spark-ignition,” says Jake McKenzie, content manager at Auto Accessories Garage. “Because of its thickness, even a small amount of diesel fuel in a gas vehicle can clog the engine’s fuel injectors, filters, and lines.” This is the best day of the week to buy a car.

Don’t Drive the Vehicle

In the unlikely event that you did put diesel into your car, and you notice your mistake before you start driving, do not start the engine. Get your car towed to a body shop right away so they can pump out the diesel, flush the fuel system and replace the fuel filters. “Time is of the essence. Even if you don’t drive the vehicle, diesel fuel in the tank will still begin to clog up the fuel system, engine, and injectors,” says McKenzie. This will likely set you back around $400 to $500.

If You Accidently Drove Your Car…

If you do start driving your car with diesel in it, you won’t get far. A gas engine can’t combust diesel fuel, so your car will move a few miles, make some strange noises, then come to a stop. McKenzie says it will cause “incredibly costly cylinder and timing issues” in your car’s engine. This type of damage could easily cost you about $4,000 to repair — sometimes up to $17,000, McKenzie says. In many cases, it can end up costing more than the value of your car.

Next, read up on these signs that your car is about to die.

Reader's Digest
Originally Published on Reader's Digest